The role of viruses or viral vaccines as possible teratogens is under investigation. Influenza A and mumps virus plus vaccines for Influenza A, Venezuelan and Western Equine Encephalitis have produced anomalies in Rhesus monkey fetuses following intra-cerebral inoculation. Bilateral cataracts were found in all fetuses inoculated with the VEE vaccine. None of the control animals used in the studies developed anomalies. Additional pregnant Rhesus monkeys are on study, inoculated with other viral vaccines normally used in humans.